Metal oxide nanomaterials and their application in solar\ud photoelectrolysis of water

0044 English OPEN
Kler, Rantej Singh;
(2014)
  • Subject: QD0415 | QD0241

Solar generated hydrogen as an energy source is green, sustainable, with a high\ud energy density. One day the majority of current fossil fuel based technology could\ud be replaced with hydrogen technology reducing CO2 emission drastically. The goal\ud in this research ... View more
  • References (174)
    174 references, page 1 of 18

    1 Introduction 1 1.1 Current Non-Solar Renewable Energy Technologies . . . . . . . . . . 2 1.1.1 Biomass Energy . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.2 Wind Turbine Technologies . . . . . . . . . . . . . . . . . . . 3 1.1.3 Hydroelectricity . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Solar Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.1 Semiconductor Fundamentals . . . . . . . . . . . . . . . . . . 7 1.2.2 Solid-State Photovoltaics (PV) . . . . . . . . . . . . . . . . . 9 1.2.3 Photoelectrochemical Solar Cells (PEC) . . . . . . . . . . . . 12 Dye Sensitised Solar Cells (DSSC's) . . . . . . . . . . . . . . . 13 Photocatalytic Water Electrolysis . . . . . . . . . . . . . . . . 14 1.3 Utilising Nanostructured Metal Oxides . . . . . . . . . . . . . . . . . 17 Photoanode Fundamentals . . . . . . . . . . . . . . . . . . . . 17 Advantages of Nanomaterial Photoanodes . . . . . . . . . . . 20 1.4 Hydrogen, Fuel of the Future? . . . . . . . . . . . . . . . . . . . . . . 23 Current Methods (CO2 Emissive) of Hydrogen Production . . 23 CO2 Neutral Methods of Hydrogen Production . . . . . . . . . 24 Hydrogen Storage . . . . . . . . . . . . . . . . . . . . . . . . . 26 Fuel Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.5 Thesis Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

    2 Analytical Methods 32 2.1 Scanning Electron Microscope (SEM) . . . . . . . . . . . . . . . . . . 32 2.1.1 Electron Source . . . . . . . . . . . . . . . . . . . . . . . . . . 34 2.1.2 Morphology Imaging . . . . . . . . . . . . . . . . . . . . . . . 35 Evehard-Thornley Detector . . . . . . . . . . . . . . . . . . . 36 2.1.3 Compositional Analysis - EDX . . . . . . . . . . . . . . . . . . 37 2.2 X-ray Diffraction (XRD) . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.3 Photo-Electrochemistry Overview . . . . . . . . . . . . . . . . . . . . 43 2.3.1 Experimental setup of a solar water splitting cell . . . . . . . 45 2.3.2 Light Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Xenon Lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Xenon Lamp, with a UV Transmitting Filter Installed . . . . 48 Cold Cathode Fluorescent Lamp light source . . . . . . . . . 49 2.3.3 Efficiency Analysis of the Photoanodes . . . . . . . . . . . . . 49

    3 Synthetic Methods 52 3.1 Electron Beam Evaporation . . . . . . . . . . . . . . . . . . . . . . . 52 3.1.1 Maintaining a High Vacuum Environment . . . . . . . . . . . 55 Rough Rotary Pump . . . . . . . . . . . . . . . . . . . . . . . 56 Turbo Molecular Pump . . . . . . . . . . . . . . . . . . . . . . 57 Titanium Sublimation Pump . . . . . . . . . . . . . . . . . . . 57 Ion Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3.1.2 Deposition Conditions and Rates . . . . . . . . . . . . . . . . 59 3.2 Anodisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.3 Vapour Transport Synthesis . . . . . . . . . . . . . . . . . . . . . . . 64 3.3.1 Vapour Liquid Solid Growth & Vapour Solid Growth . . . . . 66 3.3.2 AACVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.4 Chemical Bath Deposition (ZnO) . . . . . . . . . . . . . . . . . . . . 71

    4 Fe-Ti-O Nanotube Composite Formation via Anodisation. 73 4.1 TiO2 Nanotube Formation . . . . . . . . . . . . . . . . . . . . . . . . 74 4.2 Fe2O3 Nanotube Formation . . . . . . . . . . . . . . . . . . . . . . . 75 4.2.1 Ti Thin Film PVD on to a FTO Substrate . . . . . . . . . . . 78 4.3 Co-Evaporated Fe/Ti Thin Film, and the Formation of Nanotubes . . 80 4.4 TiO2 and Fe2O3 Nanotube Formation on Complementary Substrates . 83 4.4.1 Titanium and Iron stacked Thin Film on Conductive Glass . . 85 4.5 Photoelectrochemical Analysis . . . . . . . . . . . . . . . . . . . . . . 88 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

    5 Zinc Oxide Nanostructures formed by Vapour Transport Processing 95 5.1 Vapour Transport Nanostructure Synthesis . . . . . . . . . . . . . . . 96 5.1.1 Carbothermal ZnO decomposition . . . . . . . . . . . . . . . . 97 5.1.2 Direct Zn Powder Evaporation . . . . . . . . . . . . . . . . . . 103 5.1.3 Morphology Control . . . . . . . . . . . . . . . . . . . . . . . 106 5.2 XRD Analysis of the Crystal Structure of ZnO Nanorods Formed on a Ti Foil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 5.3 Photoelectrochemical Tests . . . . . . . . . . . . . . . . . . . . . . . . 120 5.4 Thickness Controlled Rods and Photocurrents . . . . . . . . . . . . . 125 5.5 Growth of ZnO Structures in a KOH Rich Environment . . . . . . . . 128 5.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

    6 Zinc Oxide Nanotubes and Rods on Titanium Nanotubes 135 6.1 Material Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 6.1.1 Titanium Dioxide Nanotubes . . . . . . . . . . . . . . . . . . 137 6.1.2 Zinc Oxide Nanotubular Growth . . . . . . . . . . . . . . . . 138 Initial Zinc Oxide Growth inside Tubes . . . . . . . . . . . . . 138 6.1.3 Growth of a Zinc Oxide Nanotubular Structure on a Titanium Dioxide Nanotube Framework . . . . . . . . . . . . . . . . . . 140 6.2 XRD analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 6.3 Photo-electrochemical Applications; the Splitting of Water . . . . . . 147 6.3.1 Experimental Analysis . . . . . . . . . . . . . . . . . . . . . . 147 6.3.2 Photoelectrochemical Performance of Photoanodes under different Illumination Sources . . . . . . . . . . . . . . . . . . . . 147 Photoanode Performance under Xenon light source Illumination147 Photoanode Performance under Xenon Light Illumination with a UV Transmission Filter Fitted . . . . . . . . . . . 149 Photoanode Performance under Cold Cathode Fluorescent Light (CCFL) Illumination . . . . . . . . . . . . . . . . . . 151 Comparison of Various Photoanodes . . . . . . . . . . . . . . 152 6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

    [47] Alexander Volta and Joseph Banks. I. on the electricity excited by the mere contact of conducting substances of different kinds. The Philosophical Magazine: Comprehending the Various Branches of Science, the Liberal and Fine Arts, Agriculture, Manufactures, and Commerce, 7(28):289-311, 1800.

    [48] AE Becquerel. M´emoire sur les effets ´electriques produits sous l'influence des rayons solaires. Comptes Rendus, 9(567):1839, 1839.

    [50] Akira Fujishima. Electrochemical photolysis of water at a semiconductor electrode. nature, 238:37-38, 1972.

    [51] Lionel Vayssieres. On solar hydrogen and nanotechnology. John Wiley & Sons, 2010.

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